EiR: Doping cubic boron nitride, an extreme material for power electronics and radiation detection

这个项目的重点是立方氮化硼的极端应用。氮化硼是被称为III-氮化物的半导体家族的成员，它由氮和III族元素如铝、镓和铟组成。该系列材料实现了固态照明工业，并彻底改变了微波通信。立方氮化硼是一种超宽带隙材料，对可见光透明，只吸收深紫外。它可能对电动汽车、智能电网和空间技术的电力电子设备产生变革性影响。其特殊的硬度，高导热性和耐腐蚀性也可以使这种材料在恶劣环境中取代钻石。氮化硼的研究也将有助于iii -氮化半导体的基础知识。该项目是霍华德大学和摩根州立大学这两所历史悠久的黑人学院（HBCUs）之间的合作项目。该项目使摩根大学和霍华德大学的学生能够参与到具有商业意义的尖端技术中来。该项目明确要求研究生和本科生参与“动手”研究活动。该项目将资助摩根和霍华德大学的高级设计项目，学生们将把物理电子发现转化为实际系统。该项目将鼓励少数族裔更多地参与hbcu的研究生研究项目。为了充分发挥立方氮化硼（c-BN）的潜力，需要同时具有n型和p型导通双极器件以及互补金属氧化物半导体（CMOS）逻辑。研究表明，碳氮化硼可能存在浅n型（硅掺杂）和p型（铍掺杂），这使得碳氮化硼在超宽带隙材料（UWBGs）中成为一个独特的异类。在这项工作中，我们研究了掺杂和补偿策略来评估c-BN的前景。此外，我们测量了这种材料的物理特性，如迁移率和击穿场作为缺陷形态的函数（必要时更新历史数据）。这项工作涉及小（1毫米）的商业单晶c-BN样品，以及在摩根州立大学生长的大面积薄膜。所有的测量都将通过与第一性原理密度泛函理论（DFT）计算的比较来解释，后者提供了真正基于原子物理学的理解。这项工作的挑战之一将是产生多型纯材料。为了在化学气相沉积（CVD）过程中实现这一目标，不太稳定的六方氮化硼（h-BN）多晶被蚀刻或溅射掉，从而产生立方相。我们将测试3种方法来做到这一点：i) H2蚀刻，ii)使用氟基前体和iii)离子束辅助，在单晶HPHT金刚石衬底上。表面制备和后退火将由DFT计算指导。本征点缺陷（如空位）的补偿和掺杂可能在这种UWBG材料中发挥重要作用，DFT将是理解掺杂和电输运起源的关键工具。二极管和金属-半导体-金属结构将被用作测试设备。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project focuses on cubic boron nitride for extreme applications. Boron nitride is member of the family of semiconductors known as III-nitrides, which consist of nitrogen and a Group III element such as aluminum, gallium, and indium. This family of materials has realized the solid-state lighting industry and revolutionized microwave communications. Cubic boron nitride is an ultra-wide bandgap material, transparent to visible light and absorbing only in the deep ultraviolet. It could have a transformative impact on power electronics for electric vehicles, smart grids, and space technologies. Its exceptional hardness, high thermal conductivity and corrosion resistance could also allow this material to replace diamond in harsh environments. Studies of boron nitride will also contribute to fundamental knowledge of III-nitride semiconductors. The project is a collaboration between Howard and Morgan State University, two Historically Black Colleges (HBCUs). The project enables Morgan and Howard students to participate in a cutting edge technology with commercial implications. The project explicitly engages both graduate students and undergraduates in "hands on" research activities. The project will fund senior design projects at Morgan and Howard, where students will translate physical electronics discoveries into real systems. The project will encourage greater minority participation in graduate research programs at HBCUs. To realize the full potential of cubic boron nitride (c-BN), it is desirable to have both n-type and p-type conduction enabling bipolar devices as well as Complementary Metal Oxide Semiconductor (CMOS) logic. It has been demonstrated that shallow n-type (silicon doping), and p-type (beryllium doping) are possible, making c-BN a unique outlier among ultrawide bandgap materials (UWBGs). In this work, we investigate doping and compensation strategies to evaluate the promise of c-BN. In addition we measure physical properties of this material such as mobility and breakdown field as a function of defect morphology (updating historical data as necessary). The work involves both small (1 mm) commercial single-crystal c-BN samples, as well as large area thin films grown at Morgan State. All measurements will be interpreted by comparing with first-principles density functional theory (DFT) calculations that provide a true atomic physics-based understanding. One of the challenges of the work will be to produce polytypic pure material. In order to accomplish this during chemical vapor deposition (CVD), the less stable hexagonal boron nitride (h-BN) polymorph is etched or sputtered away allowing the production of the cubic phase. We will test 3 methods to do this: i) etching by H2, ii) use of fluorine-based precursors and iii) ion-beam assistance, on single-crystal HPHT diamond substrates. Surface preparation and post-annealing will be guided by DFT calculations. Compensation and doping by intrinsic point defects (e.g. vacancies) are likely to play a strong role in this UWBG material, and DFT will be a critical tool to understanding the origin of the doping, and electrical transport. Diodes and metal-semiconductor-metal structures will be used as test devices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.